So we have a 2010 x star with the 350 mcx. Went to get it ready for the season today and put it in the water, started immediately, but no gauges or B.I.G. Display. We checked the pos and neg on the starter, engine block and battery all are in good order we are absolutely baffled as to what is going on. Any help would be greatly appreciated, thank you!
Ps. It is a dual battery system and we just charged and tested both, one was bad and we replaced it, but it is only 550 cold cranking. Could the deficit in power cause these issues or is it something else entirely?

There should be some sort of fuse or circuit breaker on a power wire going to the helm. also, make sure there are no extra wires that weren't reconnected to the battery. Maybe they fell down in teh bilge or behind a panel where you can't see. On my Supra, there was a circuit breaker in the passenger side compartment, the boat would still start, but nothing at the helm would work (gauges, etc) unless that circuit breaker was reset.